fix(sse): correct UTF-8 handling and chunking in SSE streaming\n\n- Updated splitContentIntoSegments to handle runes instead of bytes\n- Fixed buildWebUIStreamForwarder to send delta chunks instead of cumulative content\n- Ensures proper handling of multi-byte characters in SSE streams

cmd/bot/main.go

@@ -220,7 +220,7 @@ func runMessageChannel(ctx context.Context, cfg config.Config, engine *agent.Orc
 				return engine.HandleMessage(ctx, msg.ChatID, msg.UserID, msg.Text)
 			},
 			func(ctx context.Context, msg webui.IncomingMessage, callback webui.StreamEventCallback) (string, error) {
-				return engine.HandleMessageStream(ctx, msg.ChatID, msg.UserID, msg.Text, buildWebUIStreamForwarder(callback))
+				return engine.HandleMessageStream(ctx, msg.ChatID, msg.UserID, msg.Text, buildWebUIStreamForwarder(callback, cfg.WebUI.ExposeReasoning))
 			},
 			func(ctx context.Context, chatID, userID string, files []llm.InputFile) ([]string, error) {
 				return engine.UploadAndCacheFiles(ctx, chatID, userID, files)
@@ -231,16 +231,54 @@ func runMessageChannel(ctx context.Context, cfg config.Config, engine *agent.Orc
 	}
 }
 
-func buildWebUIStreamForwarder(callback webui.StreamEventCallback) agent.StreamEventCallback {
+func buildWebUIStreamForwarder(callback webui.StreamEventCallback, exposeReasoning bool) agent.StreamEventCallback {
+	const finalChunkRunes = 12
+	const finalChunkInterval = 25 * time.Millisecond
+
 	return func(event agent.StreamEvent) error {
 		if callback == nil {
 			return nil
 		}
 		switch event.Type {
-		case agent.StreamEventTypeFinal, agent.StreamEventTypeError:
+		case agent.StreamEventTypeThought, agent.StreamEventTypeToolCall, agent.StreamEventTypeToolResult:
+			if !exposeReasoning {
+				return nil
+			}
 			return callback(webui.StreamEvent{
-				Type:    webui.StreamEventType(event.Type),
+				Type:     webui.StreamEventType(event.Type),
+				Content:  event.Content,
+				Step:     event.Step,
+				ToolName: event.ToolName,
+			})
+		case agent.StreamEventTypeFinal:
+			runes := []rune(event.Content)
+			if len(runes) == 0 {
+				return callback(webui.StreamEvent{Type: webui.StreamEventTypeFinal, Content: "", Step: event.Step})
+			}
+			start := 0
+			for start < len(runes) {
+				end := start + finalChunkRunes
+				if end > len(runes) {
+					end = len(runes)
+				}
+				if err := callback(webui.StreamEvent{
+					Type:    webui.StreamEventTypeFinal,
+					Content: string(runes[start:end]),
+					Step:    event.Step,
+				}); err != nil {
+					return err
+				}
+				start = end
+				if start < len(runes) {
+					time.Sleep(finalChunkInterval)
+				}
+			}
+			return nil
+		case agent.StreamEventTypeError:
+			return callback(webui.StreamEvent{
+				Type:    webui.StreamEventTypeError,
 				Content: event.Content,
+				Step:    event.Step,
 			})
 		default:
 			return nil